This invention relates generally to dynamoelectric machines and more particularly to damping amortisseur bar vibration.
Dynamoelectric machines are utilized in many manufacturing applications. Failure of key components within a dynamoelectric machine, such as amortisseur bars, can cause lost production time, injury to personnel, and loss of capital equipment, all of which can reduce profitability. One known cause of dynamoelectric machine failure is motor airgap torque pulsations. When the frequency of these pulsations equal the torsional or ring natural frequency of the amortisseur bars, resonance occurs. In that case the vibratory stresses in the amortisseur bars may exceed a fatigue endurance limit and an amortisseur bar fatigue failure may occur. Subsequently the broken amortisseur bar may bend radially outwards under the action of centrifugal forces and contacts a stator winding end head with harmful consequences.
A factor in these failures is the fact that the inherent damping characteristic of amortisseur bars is low. As a consequence when resonance occurs, very small torque pulsations will result in a significant vibratory response, if, and when, the pulsation frequency equals the torsional natural frequency of the amortisseur bars.
In one aspect, a method for facilitating damping torsional vibrations of a dynamoelectric machine including a rotor assembly with a first amortisseur bar and a second amortisseur bar extending therefrom and terminating at an endring is provided. The method includes providing a damping assembly, and positioning the damping assembly between the first amortisseur bar and the second amortisseur bar such that the damping assembly contacts the first and second amortisseur bars, and is substantially proximate the endring.
In another aspect, an amortisseur bar damping device includes a rigid support member including a first side and a second side opposite the first side, and a first resilient member disposed to the first side and a second resilient member disposed to the second side.
In another aspect, a damping assembly includes a rotor core, a first amortisseur bar, and a second amortisseur bar. Both the first and second amortisseur bars extend from the core and the second amortisseur bar is substantially parallel to the first amortisseur bar. The damping assembly also includes a damping device contacting the first and second amortisseur bars distal from the rotor core and substantially proximate an endring. The damping device also includes a rigid support member including a first side and a second side opposite the first side, and a first resilient member disposed to the first side and a second resilient member disposed to the second side.
In another aspect, a motor includes a housing and a stator including a bore therethrough is mounted in the housing. The motor also includes a rotor shaft extending at least partially through the bore. A rotor assembly is mounted on the rotor shaft. The rotor assembly includes a rotor core mounted to the rotor shaft, and a plurality of amortisseur bars extending axially through and projecting from at least one end of the rotor core. It also includes a plurality of endrings connected to each end of the amortisseur bars distal from the core. The rotor assembly also includes an endplate attached to the core, and an amortisseur bar damping device mounted between at least two of the amortisseur bars, the amortisseur bar damping device distal the core and substantially proximate endring.
In another aspect, an amortisseur bar damping device includes a rigid support member including a first side and a second side opposite the first side. A U shaped channel is disposed longitudinally along the first side. The damping device also includes a resilient member disposed to the U shaped channel.